The present invention relates in general to a cover for a tank. It relates in particular to a modular cover which may be shipped to a site in component form and assembled at the site.
There is an increasing need for covers for enclosing in and above ground tanks which are used for storing waste materials including sewage, chemical sludge, petroleum products and the like. The materials are stored for later disposal or treatment. Such a cover must be substantially gas tight for controlling odors in the vicinity of a tank site and for trapping potentially hazardous gases.
Tanks used for storing such treatments may have a span or diameter of fifty feet or more. It is generally necessary to support a tank cover only at the edge of a tank. Because of this such a tank cover must be capable of spanning a large distance.
A tank cover is generally too large to be conveniently or cost effectively shipped in an assembled form from a manufacturer to a site where it will be used. Because of this it is generally shipped as components and assembled at the site.
Prior art tank covers made of steel are heavy and expensive even to ship in component form. Further, such covers usually require welded connections and bolted connections in their assembly. As such, skilled personnel are generally necessary to carry out the assembly, and the assembly process may be lengthy and costly.
One approach to large-span tank covers and covers for similar purposes has been a geodesic dome type structure. These covers required skilled erecting labor and were quite costly as compared to the present invention.
There is a need for a site erectable substantially gas-tight tank cover which can be assembled with a minimum of welds or bolted connections. Such a cover should preferably be modular to reduce the inventory of components necessary for building covers in a wide range of shapes and sizes, and this is an object of the present invention described below.
U.S. Pat. No. 5,050,361, assigned to the assignee of the present invention, discloses a deck structure which is weldless and is site-erectable and which includes components similar to some of the components of the present invention. The disclosure of that patent is incorporated herein by reference.